Looking to unblock users who want to use assertions with annotations added on a stack.

Fixes aws#18347 

Example:

```ts
class MyAspect implements IAspect {
  public visit(node: IConstruct): void {
    if (node instanceof CfnResource) {
      this.warn(node, 'insert message here',
    }
  }

  protected warn(node: IConstruct, message: string): void {
    Annotations.of(node).addWarning(message);
  }
}

const app = new App();
const stack = new Stack(app);
new CfnResource(stack, 'Foo', {
  type: 'Foo::Bar',
  properties: {
    Baz: 'Qux',
  },
});

Aspects.of(stack).add(new MyAspect());

AssertAnnotations.fromStack(stack).hasMessage({
  level: 'warning',
  entry: {
    data: 'insert message here',
  },
});
```

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Looking to unblock users who want to use assertions with annotations added on a stack.

Fixes aws#18347 

Example:

```ts
class MyAspect implements IAspect {
  public visit(node: IConstruct): void {
    if (node instanceof CfnResource) {
      this.warn(node, 'insert message here',
    }
  }

  protected warn(node: IConstruct, message: string): void {
    Annotations.of(node).addWarning(message);
  }
}

const app = new App();
const stack = new Stack(app);
new CfnResource(stack, 'Foo', {
  type: 'Foo::Bar',
  properties: {
    Baz: 'Qux',
  },
});

Aspects.of(stack).add(new MyAspect());

AssertAnnotations.fromStack(stack).hasMessage({
  level: 'warning',
  entry: {
    data: 'insert message here',
  },
});
```

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*